Modernization of control rooms of power plants, process industries or ships or the like often results in exchanging a panel and desk based control room to a more or less screen based control room and problems with obtaining process overview is often a result. When operating in an old type of control room, it is normally possible to see all operating objects on walls and panels and thus possible to maintain a process overview at several levels of the whole plant through parts of the plant down to individual objects. When operating on a single object it is easy to take a step back and obtain a process overview of the specific process area. In a screen based control room this advantage may be lost due to the design of the operating process displays covering just a small area of the plant, and at the large overview display showing status of the whole plant the operator easily lose orientation.
U.S. Pat. No. 5,777,896 describes a plant monitoring system based on CRT screens of different sizes. Plant information required for an operator to manipulate the plant is displayed on a first screen and plant data influenced by the manipulation is displayed on a second larger screen placed behind a manipulating and monitoring panel. The content of both displays are thus complementing each other in order to facilitate understanding of the information.
U.S. Pat. No. 5,859,885 describes a hierarchy of different layers for designing screens. Trends showing a ten minutes history of a parameter are shown on a display as a vertical meter showing the relative location of the parameter at the current time against the meter scale and a current digital value of the parameter.
ProcSee is a versatile software tool for developing and displaying dynamic graphical user interfaces, particularly aimed at process monitoring and control. The ProcSee Graphical User Interface Management System-Reference Manual is available at online.
These systems can display trends from the readings of various sensors as part of larger process and plant displays, and ProcSee is an example of software that can be used for implementing such systems. However, when the trends are displayed, the operator cannot easily understand the magnitude of the trend change, without reading the values indicated on or near an axis shown on the display.